A Leaky Wave Antenna (LWA) is a wave-guiding structure that allows energy to leak out as it propagates along a direction of propagation. FIG. 1 depicts a conventional LWA circuit as known in the prior art. Conventional LWA circuits include an input (Vi) for generating an input power 110, a matching resistance (Ri), the LWA 100 of length l, and a termination load ZL. The input, such as for example a transmitter, provides the input power 110, of which a portion is leaked out during its propagation along the LWA 100. The leaked-out power is usually referred to as the radiated power. The remaining power 120, i.e. the difference between the input power 110 and the radiated power, is absorbed by the termination load, and is referred to as the non-radiated power.
The LWA has a complex propagation constant γ which follows the equationγ=α+j*β                where        α is an attenuation constant and α≠0;        j is the imaginary unit that satisfies the equation j2=−1;        β is a phase constant with a value −k0≦β≦k0; and        k0 is a free-space wave number.        
The phase constant β controls the direction of a main radiated beam θ (measured from an axis perpendicular to a plane of the LWA), which is given approximately as θ=sin−1(β/k0). The attenuation constant α represents the leakage of radiated signals and therefore controls radiation efficiency η0 of the LWA. The LWA's radiation efficiency is provided by the following equation:
            η      0        =                            P          rad                          P          i                    =                                                  P              i                        -                          P              L                        -                          P              loss                                            P            i                          =                  1          -                      ⅇ                                          -                2                            ⁢              a              ⁢                                                          ⁢              l                                            ,                where:        Prad is the radiated power;        Pi is the input power;        PL is the non-radiated power lost in the termination load;        Ploss is the power lost along the LWA; and        l represents the length of the LWA.        
Thus the radiation efficiency η0 of the LWA directly depends on the attenuation constant and length of the LWA. To achieve better radiation efficiency, the physical length of the LWA must be sufficiently long to allow leaking out of sufficient transmitted power before reaching the termination load. For example, to achieve radiating 90% of the input power, the LWA may have to be longer than 10 wavelengths. Such a length is not practical at low frequencies, and for such reasons, most practical and finite size LWA suffer from low radiation efficiency.